Duct Weight Calculator
A takeoff tool for sheet metal quantities: enter the duct size, run length, gauge and material to get weight per foot and for the whole run, plus the insulation and lagging surface area.
Enter valid dimensions and run length, then select Calculate.
A fabricator is quoting 100 ft of 24 × 12 in rectangular duct for a 2 in. w.g. pressure class job and needs the metal weight for the material order and the hanger design.
- 1
Compute the perimeter and surface area
P = 2 × (24 + 12) = 72 in = 6 ft; area = 6 × 100 = 600 ft²
Surface area doubles as the insulation takeoff.
- 2
Pick the gauge from the pressure class
2 in. w.g. class → 24 gauge galvanized
Confirm against SMACNA tables for the actual seam and reinforcement schedule.
- 3
Weight the sheet and add the allowance
600 ft² × ~1.0 lb/ft² × 1.10 ≈ 660 lb of bare metal
The 10% allowance covers seams, locks and reinforcement — hangers and flanges are extra.
Takeaway: At roughly 6.6 lb per foot this run is routine for standard trapeze hangers, but the same perimeter in 16 gauge would triple the weight — always check lb/ft before assuming hanger spacing.
This calculator is for preliminary design guidance only. Final duct sizing, construction, and installation must be performed by qualified professionals and comply with applicable codes and standards.